Wireless networks, for example Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, may be heterogeneous networks that include “macro cells,” providing higher power/wider area coverage, and “small cells,” providing lower power/reduced area coverage. Small cells may include “femto cells,” suitable for home or office coverage and “pico cells,” for larger indoor environments such as shopping centers. A base station, for example an evolved Node B (eNB) transceiver, may be associated with each cell to provide network access to wireless mobile devices, for example User Equipment (UEs), passing through that cell coverage area.
As network traffic increases, new system enhancements are being implemented to improve bandwidth utilization and efficiency including the introduction of new carrier types (NCTs) with modified frame structures and synchronization methods. A heterogeneous network may include a mixture of eNBs, some operating with an NCT and others operating with a legacy carrier type. Some efforts to increase downlink (DL) throughput may include the reduction or removal of legacy physical downlink control channels (PDCCH) or cell specific reference signals (CRS). Further, the demodulation may rely on a demodulation reference signal (DMRS) instead of the CRS. For example the density of the CRS may be reduced in the frequency domain, the time domain or both. This may adversely affect legacy control channels that rely on CRS for demodulation, such as the physical broadcast channel (PBCH), physical hybrid-ARQ indicator channel (PHICH), physical control format indicator channel (PCFICH), and physical downlink control channel (PDCCH). This, in turn, may adversely impact backward compatibility to legacy UEs operating in an NCT environment, particularly when the NCT is configured as a standalone-carrier that is relied upon to transmit the physical signals that support initial access of the UE to the network (e.g., synchronization and PBCH, etc.).
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.